Latching mechanism



April 6, 1954 A. MASON 2,674,232

LATCHING MECHANISM Filed May 28, 1952 s Sheets-Sheet 1 POM/[R SUPPLY w.1 k fi a gm $1 INVENTOR. AVREL MASON BY WR-m ATTORflEY April 6, 1954 A.MASON 2,674,232

LATCHING MECHANISM Filed May 28, 1952 3 Sheets-Sheet 2 INVENTOR. AVRELMASO/V April 954 A. MASON 2,674,232

LATCHING MECHANISM Filed May 28, 1952 s Sheets-Sheet 3 INVENTOR. A VRELAM SO/\/ MRW ATTORNEY Patented Apr. 6, 1954 m'ronme MECHANISM Avrel-Mason, Birmingham, Mich, assignor to Bendix Aviation Corporation,Detroit, Mich., a

corporation of Delaware Application May, 28, 1952, Serial No. 290.462

151Claims. 1

This invention relates to a system for controlling the movements of anoutput member in accordance with the movements of an input member. Moreparticularly, the invention relates to apparatus for controlling themovements of input and output members in a positioning system during theperiods of system idleness, so that the system will subsequently be incondition to operate properly.

In co-pending application, Serial No. 272,591 filed February 20, 1952,by Abraham M. Fuchs, a system is disclosed for positioning an outputmember in accordance with the movements of an input member. The systemincludes a transformer having an armature which is displaced by theinput member to generate in the transformer a signal having an amplitudeproportional tothe displacement. This signal. controls the applicationof ahydraulic forceso that the force moves the output member inaccordance with thesignal amplitude. The output member is in turncoupled to the transformer windings and core for movement of, thewindingsand core in. a direction to minimizethe signal induced in thetransformer. By utilizing $110.11 a closed servomechanismloop, extremeaccuraciesare obtained in the movementof the output. member. Because ofsuch accuracies, the system, is especially useful in. guiding atool headin aceordance with the movements of a master cam.

Since a signal is generated in-the transformer only when the armaturelies within the transformer core, it is. important that therelativedisplacement between the armature and the core should neverexceed a predetermined. value. Sometimes, however, the. output membermay be inadvertently movedby unskilled operatorswhen the tool is. shut01f, sothat the armature is out of the range of satisfactory transformeroperation. For example, a janitor sweepingv a shop fioor may bump into atool headand displace the head and the transformer windingsv beyond thelimits of; transformer operation. If this should occur, the system wouldnot-. be able to function. properly until the tool. head and transformerwindings were manually adjusted in position to provide for; thegeneration of a control signal by, the transformer.

This invention provides apparatus for maintaining the relative movement.between the transformer armature and windings within safe limits eventhough the output member may be unknowingly displaced through anunusually large distance. Theapparatus operates-to couple thet ut memb rtothezinnutmembe t r ugh.

the transformer whenthe displacement between the armature and windingsof the transformer is within safe limits. As soon as the relativedisplacement between the armature and windings starts to exceed suchsafe limits, the apparatus operates to uncouple the output member fromthe-input member. Thispermits the input member to move independentlywith respect to the output member until such time as the relativedisplacement between the armature and core is again within thepredetermined value. The apparatus is simple in construction andreliable in operation for all conditions that may be encountered.

Anobject of this invention is to provide apparatus for operating with asystem which accurately positions an output member in accordance withthe movements of an input member.

Another object of the invention is to provide apparatus for use inconjunction with the positioning system disclosed above to maintain thesystem operable at all times.

A further object is to provide apparatus of the above character formaintaining a positioning system operable at all times even when theoutput member of the system is moved through unusually large distancesbyunskilled operators.

Still another object is to provide apparatus of the above character foroperating in conjunction with a positioning system to maintain thesystem in readiness for proper operation regardless of any movementsthat components in the system may undergo during the periods of systemidleness.

A still further object is to provide apparatus ofthe above character forpositioning a tool head in accordance with the movements of a master camand for protecting the tool head against damage from unusualmovementsthat may be inadvertently imposed on the head by unskilled operators.

Other objects and advantages will be apparent from a detaileddescriptionof the invention and from the appended drawings and claims.

In the drawings:

Figure 1 is a schematic diagram, partly in block form and partlyinsection, illustrating one embodiment of apparatus for positioning anoutput, member in accordance with the movementsof an input member;

Figure 2 is an enlarged perspective view of certain components shown inFigure 1 and iliustrates these components in further detail;

Figure ,3 is an enlargedsectional view illustrating an alternateposition for certain me- 3 chanical components shown in Figures 1 and 2to maintain the embodiment of Figures 1 and 2 in an operable conditionat all times; and

Figure 4 is a diagram of curves illustrating the operation of certainelectrical components shown in Figure 1.

In one embodiment of the invention, a cam I positions an input membersuch as a drive rod I 2 slidably mounted on uprights I4 which extendfrom an output member, such as a tool head IS. The rod I2 is yoked as atI8 and each leg of the yoke is provided with a disc 20 adapted tonormally extend into a cut provided at the intersection oi the two legsin a bell crank lever 22. The cut is fairly steep at one side 24 andmore shallow at the other side 26, and is integrated by an intermediateportion having a predetermined length, as will be disclosed in detailhereinafter.

The bell crank lever 22 is pivotable at an intermediate position on ahousing 30 which supports for movement therewith the armature 32 of atransformer, generally indicated at 34. A spring 36 is fastened at oneend to the housing and at the other end to a leg of the bell crank lever22 at the outer position of the leg. A lug 38 extends from the end ofthe leg fastened to the spring 36 and, in one position of the lever 22,engages a. stop 40 which forms a part of the tool head I6. An adjustingscrew 42 extends through a threaded socket in a flange jutting out fromthe housing 30 and presses against the lever 22 adjacent the position atwhich the spring 36 is fastened to the housing 30.

In like manner a bell crank lever 44 similar in. construction to thelever 22 is disposed on the housing 36 in opposite relationship to thelever 22. The lever 44 is pivotable on the housing 30 at approximatelythe same position as the lever 22, so that the rod I2 is able to moveonly arelatively small distance in either direction relative to thelevers without tripping one of the levers. A spring 46 is fastened tothe lever 44- and the housing 30 in a manner similar to that disclosedabove for the spring 26. A lug 48 is provided on the lever 44 forengagement with astop 50 extending from the tool head I6, and a stud 52is adjustably supported by the housing 30 for engagement with the lever44.

The armature 32 of the transformer 34 is made from a suitably magneticmaterial and is: slidable within a non-magnetic core 54 suitably securedto the tool head I6. A primary winding: 56 and a secondary winding 50are interleaved on the left side of the core 64, and a primary winding66 and a secondary winding 62 are interleaved in a similar manner on theright side of the core. The windings E36 and 58 are similar to thewindings 60 and 62 respectively.

The inner terminals of the primary windings 56 and 60 are connected toeach other and the outer terminals are connected to a signal generator64. Connections are made from the inner terminal of the secondarywinding 58 to theouter terminal of the secondary winding 62 and from theouter terminal of the winding 58 and, the inner terminal of the winding62 to the input terminals of an amplifier 66. The output from theamplifier 66 is introduced to a detector 68 which has its output appliedeither directly' or through amplifiers (not shown) to the outerterminals of a pair of windings and 12 forming part of a torque motor,generally indicated. at 14.

The inner terminals of the windings 10 andv 12 are connected to anoutput terminal of a.

direct power supply 16. The windings I0 and I2 are disposed on oppositelegs of an armature 18 pivotable on a centrally disposed pin. Thearmature I8 is made from a suitably magnetic material and is separatedby relatively small air gaps from oppositely disposed yokes 82 and 84forming part of a horseshoe magnet (not fully shown). Pistons 66 and 88are pivotably supported on the outer ends of the armature 18. The piston86 is slidable in a sleeve 90 having an inlet conduit 92, an outletconduit 94 and connecting conduits 96 and 98. Spools I00, I02 and I04are provided on the piston 86 adjacent the conduits 96, 92 and 94respectively. The spools I02 and I04 are connected by a portion I06having a curved indentation, as fully disclosed in co-pendingapplication Serial No. 222,591 filed April 24, 1951, by Shih-Hing Lee.

The curved indentation of the connecting portion I06 is provided tocompensate for the force opposing the opening of the valve, so that thevalve will be operated upon the application of a relatively small torquefrom the armature I8. The force opposing the opening of the valve isproduced between the conduit 96 and the spool I00 as the spool movesaway from its position blocking the conduit.

In like manner the piston 88 is provided with spools corresponding tothe spools I00, I02 and I04, respectively, and is slidable in a sleeveI08 similar to the sleeve 90. The sleeve I08 is provided with inlet andoutlet conduits corresponding to the conduits 92 and 94, respectively,and with connecting conduits H0 and H2 similar to the conduits 96 and98, respectively. The conduit 96 communicates with the conduit II2 toform a channel II6 leading to the right side of a piston H8 in a ram,generally indicated at I20. Similarly, the conduits 98 and H0communicate with each other to form a channel I22 leading to the leftside of the piston H8. The piston H8 is fastened to a rod I24 adapted todrive an output member such as the head I6 of a tool (not shown). Thehead I6 carries a cutter I26 for producing on the face of a workpieceI28 a pattern determined by the movements of the head. The head I6 isalso coupled to the core 54 and the windings 56, 58, 60 and 62 toproduce a displacement of the core and windings.

In its neutral position, the armature 32 is so positioned relative tothe secondary windings 58 and 62 that voltages of equal magnitude areinduced in the windings by the current flowing through the primarywinding from the signal generator 64. Since the voltages induced in thesecondary windings have opposite polarities, they are cancelled whenintroduced to the amplifier 66. When the armature 32 is displaced fromits intermediate position, voltages of unequal magnitude and oppositepolarity are induced in the windings 5B and 62, and the differencebetween these voltages is amplified and detected.

For relatively small displacements of the armature 32 to either side ofits neutral position, the output voltage produced by the amplifier 66 issubstantially proportional to the armature displacement. This resultsfrom the symmetrical disposition of the windings 56, 58, 60 and 62 onthe nonmagnetic core 54. For example, in one model that has been used,the relationship between the output signal and armature displacement issubstantially linear for displacements up to mils from either side ofthe neutral position. In other models, a substantially linearrelationship exists gar-era ster giaatispaaae uturret-deviat on fromtruelinearityis slightlv' greater than in the model disclosedab'ove.,fTIie substantially linear portions of the curves of transformerresponse vs.

armature displacement areillustrated at I30 and is; in -;Figure' 4 forarmature displacements to either side of the neutral position.

As the armature continues to move beyond the region of linear response,its output signal in- 'is actually starting to decrease. The portions oftheresponse curves illustrating the; actual decline or the qutputsighnsare illustrated at I38 and M in Figure 4. At relatively greatdisplacements of the armature 32 to either side of its neutral position,the amplitude of the output signal generated by the transformer 34actually declines to zero.

H The transformer 3'4'ordinarily operates in the region of linearresponse. After being amplified and detected, the output signal isapplied as proportionate direct currents to the windings I0 and I I2. Apositive current flows through one winding from the detector 68, and anegative current of equal magnitude flows through the other winding fromthe detector. Thepositive current through the first winding aids thecurrent flowing through the winding from the power supply It, but thenegative current through the other winding opposes the current fromthepower supply. The

resultant unbalance 'ofthe currents through the windings causes thearmature I8 to be pivoted in a direction and through an angle determinedby theunbalance. I

When the armature l8 pivots in a clockwise direction, it moves thepiston 86 upwardly and the piston 88 downwardly. The upward movement ofthe piston 86 causes the spools I00 and I02 to move away from theirpositions blocking the conduits Stand 98, respectively. As a result, acontinuous circuit is established which includes the inlet conduit 92,the connecting conduit 96, the channel II6, the ram I20, the channelI22, the connecting conduit 98 and the outlet conduit 94. The'fluidflowing throughthe continuous circuit acts uponthe piston H8 in the ramI20 to move the piston to the left. The rate at which the piston I I8moves at any instant isdetermined by the distance through which thepiston 86 has moved upwardly at that instant, since this distancecontrols the amount of fluid flowing through the ram I20. Similarly, thepiston IIB moves to the right when the armature I8 is pivoted in acounterclockwise direction. I

When the piston I I8 moves to the left'or right in Figure 1, it producesa corresponding movement of the tool head It and the cutter I26 so thatthe cutter cuts the workpiece I28 in a pattern determined by themovements of the cam It. The tool head I6 also drives the core 54 andthe windings of the transformer 34in a direction to minimize the outputsignal induced in the transformer. In this way, the movements of thecutter I25 relative to the workpiece I28 are controlled by a closedservomechanism loop which is always operating to'r'educe to zero anydifference between the movements of the armature 3'2 and the core 54.Because of the closed servomechanism loop,

the relative displacleinent between the armature -32 and the core 54' isalways in the order of amil 'orlessduring the cutting operatiomeventhough the cutter I26 may be moving ss-much-as' several inches fromits neutral position. v i

As previously disclosed, the output signal from the transformer 34actually declines to zero if the armature 32 becomes considerablydisplaced from its neutral position. If thearinatureshould be would haveto be'manua llymoved in order to bring the system within the operatingrange of the transformer. Once the relative displacement was reduced sothat an output .inthe portion I38 or Hi8 could be produced in thetransformer 34, the transformer would produce a signal upon theoperation of the positioning system. This signal would be utilized bythe'system shown in Figure 1 to reduce the relativedispl'a'cementb'etween the armature and core so that thetransformer'would thereafter operate atthe beginningof "the linearregions I39 and I32.

This invention provides'apparatus for maintaining the relativedisplacement between the ar nature 32 and the core 'E'IWithintheoperating range of the transformer at all times. For "relativedisplacements in which an output signal is produced by the transformer,the disc '20 on each leg of the yoke I8 is positioned within the cut inthe bell crank lever 22 defined by the walls 24 and 26 and thecorresponding 'cut in the lever 44. This causes the disc 28 to serve asa detent and to operatively engage the levers 22 and! for movement ofthe housing 3D to the right orleft "in accordance with the movements ofthe rod I2. Since the armature 34 is supported by the housing 30, thearmature is similarly "displaced relative to the core 54.

Since the core 54 and'the windings on'the core are connected to the toolhead I6, 'the'displacement between one of "the uprights I4 and thehousing 36 gradually decreases asthe armature 32 moves from its neutralposition with respect to the core 5A. For example, the housing 30gradually approaches the left upright I4 in Figure 1' as the armature 32is displaced to the left. At a displacement between the armature andcore corresponding 'to an output signal "illustrated at It-2, thehousing 30 presses against the left upright I4. If the relativedisplacement between the armature 32 and'the'co'refifi thereafterincreases, th disc 20 exerts an increased force on the bell crank lever22 andcauses the lever to pivot into an alternate position. Thisalternate position is illustrated in Figure 3 for the lever 22.

When the lever 22 pivots into the position illustrated in Figure 3, itcauses the housing30 and the armature 32 to becomeoperatively uncoupledfrom the drive rod I2. Because of this uncoupling, any subsequentmovements of'the rod E2 in a direction to increasethe displacement between the armature and the core54- are not transmitted to the armature.The uncoupling continues until the relative displacement between thearmature and the core-dec'reases-belowthe'critical Upon such a decreasein displacement, the disc presses against the side 26 of the cut in thelever 22 and causes the lever 22 to pivot back into the positionillustrated in Figure 1. The rod I2 then drives the housing 30 and thearmature 32 until such time as the critical distance is again reached.

During the time that the bell crank lever 22 is uncoupled from thearmature 32, the lug 38 on the bell crank lever engages the stop 40extending from the tool head l6. This engagement causes the housing 30to follow any movements of the head l6 when the head moves in adirection tending to increase the displacement between the armature 32and the core 54. The engagement between the housing 30 and the tool head16 is broken when the lever 22 pivots back into the position indicatedin Figure l as a result of a decrease in the displacement between thearmature and cor below the critical value indicated at I42 in Figure 4.

As previously disclosed, the displacement between the armature 32 andthe core 54 is generally not greater than a mil during the operation ofthe positioning systems. If, however, the tool head should be jarredwhile the system is operating, the displacement between the armature 32and the core 54 camiot exceed the critical distance corresponding to thesignal I42 because of the operation of the bell crank levers 2'2 and Mand their associated components. Since the armature 32 and core 54 arealways positioned relative to each other for the production of an outputsignal, the system operates, after its period of idleness, to quicklyreduce the relative displacement to a nominal and normal value. fhisnormal value is at the beginning of one of the linear regions 30 andI32.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore to be limitedonly as indicated by the scope of the appended claims.

What is claimed is:

1. In combination, a motion sensor including first and second membersmovable relative to each other through a first range from a nullposition to generate a signal having an amplitude proportional to theirrelative movement, input means, I

means for providing a co-operative engagement between the input meansand the first member of the motion sensor for relative movements of apredetermined magnitude between the first and second members greaterthan the first range and less than that in which th motion sensorgenerates an operable signal, output means having a co-operativeengagement with the second memher in the motion sensor and operativeupon introduction of the generated signal to move in accordance with themovements of the input means, and means operative upon a relativemovement of the predetermined magnitude between the first and secondmembers to disengage the means providing a co-operation between theinput means and the first member.

2. In combination, a motion sensor including first and second membersmovable relative to each other through a first range from a nullposition to generate a signal having an amplitude proportional to theirrelative movement, input means, latching means adapted to be driven bythe input means, means adapted to be driven by the latching means and todrive the first member in the motion sensor in accordance with themovements of the input means, output means connected to the secondmember in the motion sensor and operative upon introduction of thegenerated signal to move in accordance with the movements of the inputmeans, and means for disengaging the latching means upon a predeterminedrelative movement between the first and second members greater than thefirst range and within the operable limits of the motion sensor to freethe first member from movement with the input means.

3. In combination, a motion sensor including first and second membersmovable relative to each other through a first range from a nullposition to generate a signal having an amplitude proportional to theirrelative movement, input means, detent means on the input means toprovide a displacement of the first member in the motion sensor, meansfor engaging the detent means for relative displacements of apredetermined magnitude between the first and second members greaterthan the first range and within the signal-generating limits of themotion sensor, output means adapted to be displaced in accordance withthe signal from the motion sensor and to produce a correspondingdisplacement of the second member in the sensor in a direction tominimize the signal, and means for disconnecting the engaging means fromthe detent means upon movements of at least the predetermined magnitudebetween the first and second members so as to provide a free movementbetween the input and output means.

4. In combination, a motion sensor including first and second membersmovable relative to each other through a first range from a nullposition to generate a signal having an amplitude proportional to theirrelative displacement, input means, detent means on the input means,means for operatively engaging the detent means for displacements of apredetermined magnitude between the first and second members greaterthan the first range and within the operable limits of the motionsensor, output means adapted to be displaced in accordance with theamplitude of the generated signal and to move the second member in adirection relative to the first member to minimize the generated signal,means for disconnecting the engaging means from the detent means upon arelative movement of at least the predetermined magnitude between thefirst and second members, and means for reinstituting the connectionbetween the detent means and the engaging means upon a relative movementbetween the first and second members to return their relativedisplacement to within the predetermined limit.

5. In combination, detent means, means for engaging the detent means formovements corresponding to its own movements, input means operative tomove the detent means in accordance with its own movement, a motionsensor including first and second members movable relative to each otherthrough a first range from a null position to generate a signal havingan amplitude dependent upon their relative displacement, means connectedto th first member in the motion sensor and to the engaging means formovement of the first member for displacements of a predetermined valuebetween the first and second members greater than the first range andless than that in which the motion sensor generates an operable signal,output means connected to the second member and adapted to be displacedin accordance with the amplitude of the generated erative upon areduction in the relative displacement between the first and secondmembers to that within the predetermined value to couple the firstmember to the input means for a movement of the first member with theinput means.

12. In combination, a motion sensor including first and second membersmovable relative to each other to generate a signal, input means,latching means adapted to move the first member of the motion sensor andadapted to be driven by the input means for relative movements betweenthe first and second members of the motion sensor of a predeterminedmagnitude within the signal generating limits of the sensor, outputmeans operative upon introduction of the signal generated by the sensorto move the second member of the sensor in a direction to minimize therelative displacement between the first and second members, means fordisengaging the latching means upon a relative displacement of thepredetermined magnitude between the first and second members of themotion sensor to uncouple the input means and the first member in themotion sensor, and means for re-engaging the latching means upon areduction in the relative displacement between the first and secondmembers of the motion sensor to a magnitude less than the predeterminedvalue to produce a movement of the first member in the motion sensorwith the input means.

13. In combination, a motion sensor including first and second membersmovable relative to each other within predetermined limits to generatean operable signal, a housing for supportthe first member of the motionsensor, a bell crank lever having a recess portion and pivotablysupported on the housing, tension means connected between the bell cranklever and the housing to maintain the lever in an operative position,input means, detent means on the input means and positioned within therecess portion of the bell crank lever for relative movements of lessthan the predetermined value between the first and second members of themotion sensor, output means connected to the second member of the motionsensor and operative upon introduction of the signal generated by thesensor to move the second member in a direction to minimize the relativedisplacement between the first and second members, means for producing apivotal movement of the bell crank lever, upon a relative displacementof the predetermined value between the first and second members of themotion sensor, to free the detent means from the recess portion of thelever, and means for pivoting the bell crank lever into an engagementbetween the recess portion and the detent means upon a reduction of therelative displacement between the first and second members of the motionsensor to a magnitude within the predetermined value.

14. In combination, a bell crank lever having a recess portion, an inputrod, a disc connected to the input rod and positioned within the recessportion of the bell crank lever for movement of the lever in accordancewith the movements of the input rod, a motion sensor including first andsecond members movable relative to each other through a first range froma null position to generate a signal having an amplitude proportional tothe relative movement, a housing for supporting the first member of themotion sensor and adapted to move with the input rod for relativemovements between the first and second members of the motion sensor of apredetermined magnitude greater than the first range and within thesignal-generating limits of the sensor, output means connected to thesecond member of the motion sensor and operative upon introduction ofthe signal generated by the sensor to move the second member in adirection to minimize the relative displacement between the first andsecond members, means operative upon 'a relative displacement of thepredetermined magnitude between the first and second members of themotion sensor to free the disc from the recess portion of the bell cranklever, and means operative upon a reduction in the relative displacementbetween the first and second members to a magnitude within thepredetermined value to position the disc within the recess portion ofthe bell crank lever.

15. In combination, a bell crank lever having a recess portion, an inputrod, a disc attached to the input rod and positioned within the recessportion of the bell crank lever for movement of the lever in accordancewith the movements of the input rod, a motion sensor including first andsecond members movable relative to each other through a first range froma null position to generate a signal having an amplitude proportional tothe relative movement, a housing for supporting the bell crank lever andthe first member of the motion sensor and adapted to move with the inputrod for relative movements between the first and second members of thesensor of a predetermined magnitude greater than the first range andwithin the signal generating limits of the sensor, output meansconnected to the second member of the motion sensor and operative uponintroduction of the signal to move the second member in a direction tominimize the relative displacement between the first and second members,a lug connected to the output means, means on the output means forengaging the housing upon a relative displacement of the predeterminedmagnitude between the first and second members of the motion sensor tofree the disc from the recess portion of the lever and to dispose thelever against the lug, and means operative upon a reduction in therelative displacement between the first and second members to amagnitude within the predetermined value to position the disc within therecess portion of the lever and to free the lever from engagement withthe lug.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,357,790 Turchan et a1. Sept. 5, 1944 2,373,332 ONeill Apr.10, 1945 2,437,603 Hornfeck Mar. 9, 1948 2,533,040 Petrak Dec. 5, 1950

